I think my hamster has psychological issues.

Question
My hamster (Zac) has started acting very strange, he is either very friendly and tame as he was when i brought him, frightened and skitish and runnig round in circles or lying flat against the floor of his cage for hours and not moving. My other hamster (tiggy) died a few months ago and I was wondering if he misses her they are both syrian hamsters and had seperate cages altough they lived next to each other. he eats and drinks normally and does exercise when he acts normally. I have kept hamsters on and off for 15 years and have never had one that has acted so strange. plaese help, Gemma  

Answer
Dear Gemma,
thank you for your question.
Zac definitely doesn't miss Tiggy, Syrian hamsters are strictly solitary and don't need ot even want friends.
Is there anything that could scare him, maybe some kind of noise or something that happens only for a few hours?
Another thing I can imagine is that he is in pain from something, for example a tumor. It really reminds me of irregualr behaviour caused by a brain tumor, but I have never heard of this with hamsters. I'd see a vet with him, just to rule anything medical out. If you need to find a rodent vet near you, here's a good website:
http://www.vin.com/vetquest/index0.html
I'm sorry that I cannot give a definite answer, but I really haven't seen something like this with one of my hamsters or heard of it.
Best wishes
Jennifer